Python web testing for the Ruby programmer

Ruby has a couple of well-known libraries for unit testing, mocking and stubbing HTTP interactions. My typical toolset includes RSpec, WebMock and VCR. I had the chance to work on a Python project recently and did some investigation into similar libraries for Python.

General testing libraries

The two most popular python test libraries + runners are py.test and nose. A neat feature of py.test is that is gets by with only the builtin ‘assert’ keyword: the test runner expands assertion failures to show exactly how the assertion failed e.g.:

as these methods cannot be replaced in CPython. You’ll need to write a wrapper function and mock that out instead in your tests.

Web testing

The werkzeug WSGI library includes simple utilities to make request testing as easy as with rack-test. Another library I’m a big fan of is HTTPretty, which is similar to Ruby’s WebMock or FakeWeb. Finally, Ruby’s VCR gem is invaluable for recording real HTTP interactions. A port exists on python called vcr.py.